Projection welder



Aug. 6, 1940. E. G. BIEDl-:RMAN

PROJECTION WELDER Filed July 19, 1938 2 Sheets-Sheet. l

Aug' 6,1940 E. G. BIEDERMAN 2,210,056

PROJECTION WELDER' Filed July 19, .1938 2 Sheets-Sheet 2 ATTORNEYJPatented Aug. 6, 1940 PATENT GFFICE 2,210,056 PROJECTION wELDEn EdwardG. Biederman, Detroit, Mich., assignor to General Motors Corporation,Detroit, Mich., a corporation of Delaware Application July 19, 1938,Serial No. 220,071

3 Claims.

This invention relates to projection welding on the y.

In the drawings:

Fig. 1 is a side elevation of the machine.

Fig. 2 is a cross section through the carrier showing the front of thetwo Welders.

Fig. 3 is a section on the line 3-3 of Fig. 1.

Fig. 4 is a detail elevation showing a part of one of the Welders.

Fig. 5 is a plan View of the work.

Projection welding is very old and consists of using punched out pointson one or both pieces of sheet metal and then applying large padelectrodes one above and one below the work. The sheets will onlycontact at the points and, consequently, the current only passes throughthe sheets at the points and the work is welded and fused together in a.plurality of spot welds.

'I'his projection welding has always been done, so far as I am advised,on stationary machines. It is the purpose of the present invention toprovide an arrangement whereby the work can be properly punched with theprojections, placed on a carrier in assembled relation and welded whilethe carrier moves continuously along.

Referring to Fig. 4: It will be seen that here three pieces of stripmetal are shown. The center piece has projections I and 2 rpointingupwardly and downwardly respectively. A carriage or plate 3 of copperrides over the rolls 4 which contact the plate through wear plates or`strips of fiber or other insulating material strips 5. The copperportion of the plate contacts the copper brushes 6 which are part of thesecondary circuit as shown in Fig. 1. The chain 'l carries the workplate along,vthe chain being located in the center of the carrier andcarrying a socket 8 in which ts a roller 9 carried bythe insulatingblock I0 in the carriage.

At the proper time, as the carriage comes along, a valve (not shown) maybe tripped by the carriage or operated by hand to send fluid into thecylinders II tov cause the pistons I2 to move downwardly pressing thevertically guided cross heads I3 downwardly. These cross heads areguided in the grooves formed by the strips I4. This is shown in Fig. 3.To each of these cross heads is pivoted four parallel arms or links I6.Springs I1 bearing against lugs I8 on the cross 50 heads and against twoof the parallel arms IE tend to keep the arms swung to the right in Fig.4.

Then, as the piston comes down, it brings the electrode pad I9 intocontact with the work.

These lugs also act as stops for the links on the .55 return stroke.This electrode pad is connected through the laminated bus bar 20 withthe secondary circuit, as shown in Fig. 1. When the upper electrodegrips the work and forces it against the lower pad 3, the electrodesgrip the Work and travel a slight distance with it which will be seen 5by comparing the dotted lines of Fig. 1 with the full lines showntherein. As soon as the uid is released and reversed in the cylindersIl, the upper electrode pad will be lifted oi the work and the springsI'I will return the pad to the right 10 hand position.

This invention is useful, for instance, in Welding reinforcing strips tothe floor pans for automobile bodies, such as shown in Fig. 5, where a.longitudinal strip 2I is welded to the cross strip 16 22 which, in turn,is welded to the floor pan 23.

Many other uses may be found for it.

I claim:

1. In a welding machine, a carriage moving only in one direction andarranged to carry work 20 provided with a multiplicity of punched outpoints for projection welding, said carrier iorming an electrode pad ofconsiderable contact area to bridge all the said points and forconnection with part of the secondary circuit, an electrode 25 pad ofsubstantially the same area movable upon the opposite side of the workand connected with said secondary and arranged to travel a limiteddistance along with the work carrier while the projection welding istaking place, iiuid operated 30 means for pressing the pad against thework to cause the work to carry the pad along with the work andpermitting travel of the Work while said pad is upon the work, and meansfor returning the said pad to its initial position.

2. In a welding machine, a carriage, means for continuously moving thecarriage, said carriage forming an electrode pad, commutator brusheslocated along the path of travel of the carriage and in the secondary ofa welding circuit and 40 arranged to wipe said electrode pad, a secondelectrode pad for bearing down on the work on the opposite side whilethe carriage moves continuously along, said pad arranged for a limitedtravel with the work while it moves along, the said pad also beingylocated in said secondary circuit, supporting means for said second padcomprising a cross head movable substantially perpendicularly to thepath of travel of the carriage and thrust means between the cross head50 and pad having movementwith both a perpendicular and parallelcomponent with respect to the pad and permitting the pad to move alongwith the work while the welding is being done.

3. In a welding machine, a continuously movcircuit, *supporting meansfor said pad comprising a cross head movable substantiallyperpendicularly to the path of travel oi the carriage and thrust meansbetween the cross head and pad in the form of links permitting the padto move along with the work while the welding is being done.

EDWARD G. BIEDERMAN.

